The present invention generally relates to the enhancement of air flow into the air intake throat of an internal combustion engine at selected times during operation of the engine, particularly during engine start-up and under abnormal idle conditions as needed until adequate air flow into the engine has been established. An air intake valve assembly is positioned at a location downstream of the throttle valve of the engine in order to provide a flow of ambient air into the air intake throat at this location during the start-up mode of the engine, which flow of ambient air is blocked by operation of the intake valve assembly by the time the engine is in its open throttle mode.
Internal combustion engines have been developed which do not include what is generally known as a carburetor assembly. Instead, fuel injection systems are provided which may be either of the high pressure type or of the low pressure type. Low pressure fuel injection systems can be particularly well suited for two-cycle engines, and especially for internal combustion engines that are incorporated into marine outboard motors. These low pressure fuel injection systems are designed to eliminate the need for high pressure components, including high pressure fuel injectors, a high pressure fuel pump, and a constant fuel pressure regulator. Examples of these types of low pressure fuel injection systems are found in Staerzl U.S. Pat. No. 4,305,351 and No. 4,763,626, the subject matter thereof being incorporated by reference hereinto.
Whether high pressure or low pressure fuel injection systems are utilized, it is important to have the proper mixture of air and fuel for each particular mode of engine operation. Providing proper air flow during the various operational modes can present an especially difficult problem for two-cycle engines which tend to idle poorly, due in part to limited air supply paths in many two-cycle engines. Generally speaking, the primary source of air for the fuel and air mixture in these types of engines is through the throttle valve, which is typically closed or substantially closed during normal engine start-up and/or engine idling modes.
Various fuel and air routing paths have been proposed or attempted in order to provide the proper fuel and air mixture at each engine operation mode. At times the proposed systems are substantially complex and may require monitoring of engine parameters and inputs to the engine in an attempt to provide the proper mixtures. Often, these types of arrangements introduce complexities which may decrease long-term reliability. Complexity can be particularly troublesome in engines that are used under rugged conditions.
Another problem faces the manufacturers of engines and is especially prevalent for an engine which has its cylinders in a generally vertically stacked array, such as is the case in various marine outboard motor engines. With vertically stacked cylinders, there is a tendency, due the influence of gravity, for residue fuel to "puddle" along the portion of the crankcase walls which is lower than the rest of the particular crankcase. This condition can be aggravated because of the general tendency for the lower cylinders to receive a greater flow of fuel than the upper cylinders. This can lead to an unduly enriched fuel-air mixture in the lower cylinder or cylinders to the extent that even greater puddling can develop in the lower crankcase or crankcase chambers.
Because of these types of puddling problems, bleed systems have been developed for various engines. In earlier day marine outboard engines, this puddled fuel would be permitted to bleed from the crankcase and into the lake or other body of water on which the marine engine was operated Ecological considerations have resulted in the phase-out of this practice, and puddled fuel is typically recycled from low point locations in the crankcase generally adjacent to the reed block for one cylinder and to an inlet located in the sidewall of another cylinder at which the excess fuel can be burned. Usually, this type of recycling results in movement of puddled fuel during the start-up mode, resulting in an excessively rich fuel mixture that is burned during initial engine operation, which is usually manifested in the development of blue exhaust smoke which persists until the excess recycled fuel is burned off. This is not especially desirable, and means have been sought for removing the puddled fuel without either damaging the environment or creating an unpleasant trail of smoke.
By proceeding in accordance with the present invention, an arrangement is provided wherein a supplemental flow of air is introduced into the air intake throat of the engine at a location downstream of the throttle valve of the engine. The supplemental air flow is automatically provided while the engine is in its start-up mode and under abnormally slow idle conditions. This flow of supplemental air is cut off during normal operation or acceleration. By this arrangement, the supplemental source of air is provided when the throttle valve is closed or substantially closed, and the supplemental air flow ceases at least at those times during which the throttle valve is fully opened. When desired, the invention can be supplemented with a recycling assembly by which puddled fuel is directed for entry into the engine throat at this location downstream of the throttle valve and such that the recycled fuel enters after start-up in order to thereby burn the recycled fuel under engine operation conditions that are less likely to result in the development of concentrated exhaust smoke.
It is a general object of this invention to provide a mechanism for providing improved start-up conditions for an internal combustion engine.
Another object of the present invention is to provide an improved mechanism for stabilizing an internal combustion engine when abnormally low or slow idle conditions develop.
Another object of the present invention is to provide an improved starting enhancer and stabilizer for two-cycle engines by leaning out the fuel-to-air mixture during times of starting and abnormal idling.
Another object of this invention is to provide an assembly for supplementing the flow of ambient air into a low-pressure fuel injection system.
Another object of the present invention is to provide an improved apparatus and method for enhancing starting and stabilizing two-cycle internal combustion engines by automatically supplementing air flow thereinto at time when such supplemental air flow is desirable.
Another object of the present invention is to provide an improved apparatus and method for recycling puddled fuel from an engine crankcase to a suitable location in a fuel injection system.
Another object of the invention is to provide means for relieving an abnormally slow engine idle condition which can occur when the throttle is rapidly closed while the engine is running at a high rpm.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.